Fig. 1.

Tissue-specific and inducible Cre-mediated expression of GFP in cardiomyocytes. a Generation of tamoxifen-inducible double transgenic animals (MerCreMer/mTmG). Schematic illustration of MerCreMer and mTmG construct to generate bi-transgenic animals. MerCreMer mice are crossed with mTmG animals to trace the lineage of GFP-positive cells in the cardiomyocyte. b Ubiquitous expression of tdTomato and cardiomyocyte-specific expression of GFP demonstrated in mouse tissue from a MerCreMer x mTmG cross at necropsy. Fluorescent, F1 generation littermates were euthanized and imaged at 12 weeks of age. All sections were recorded during a single imaging session using the same exposure times. GFP expression is limited to the cardiomyocyte whereas tdTomato is brightly expressed in all the other cells. The images of different muscle tissues were adjusted equally for brightness and contrast. All other images are shown without post-acquisition processing. Scale bars, 100 μm. c Cardiomyocytes were isolated from adult transgenic mice. The left panel shows the isolated GFP expressing cardiomyocytes under the 20X objective, the right panel shows the bright field image of the isolated single cells. Scale bars: 30 µm